LABORATORY AND SPACE EXPERIMENTS TO STUDY PREPLANETARY GROWTH

The present models for the origin of the solid planetary bodies in the solar system distinct between two major phases: (1) the aggregation of dust particles and clusters in the solar nebula driven by low-velocity mutual collisions and attractive interparticular forces as the responsible process for the growth of km-sized objects and (2) the accretion of planetary cores and planets due to intermediate and high-velocity planetesimal collisions and gravitational attraction. The theoretical considerations and their predictions for the development of the solid bodies in the early solar system strongly depend on a couple of assumptions, the validity of which can only be proven experimentally. Among the processes to be determined empirically, the low velocity collision behavior of single dust grains and aggregates including simulation experiments on the long-term dust aggregation (to deduce sticking and fragmentation efficiencies as well as morphological structures of growing dust aggregates) and intermediate/high-velocity imp act pro ces ses (to study the efficiency of planetary accretion) seem to be of crucial importance for the applicability of the models. International activities in the field of laboratory and space research to study pre-planetary growth processes are reviewed in this article and forthcoming experiments are presented.